How many direct magnetic courses can there be between two points? Sometimes the answer is three. How many can possibly be right? Actually, all of them.
Mag Course mismatches
I looked at the arrivals into Chicago OHare and noticed something peculiar. Both the BENKY ONE and BRADFORD FIVE arrivals have a transition route from Kirksville VOR (IRK) to LOAMY intersection. But the BENKY arrival shows a course of 068 degrees while the BRADFORD arrival shows 059. I put IRK direct to LOAMY in my GPS ... and got a third course of 064.
Key Takeaways:
- Multiple magnetic courses can exist for the exact same two points due to the complexities of magnetic variation.
- These discrepancies arise because magnetic north shifts over time, and various navigation systems (like VORs, airports, charts, and GPS units) are updated with differing magnetic variation models and at different frequencies, leading to inconsistent application.
- Despite the different displayed magnetic courses, all methods describe the same true ground track, making these variations operationally acceptable for navigation as the actual flight path remains consistent.
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